Multicast is a technique for sending data efficiently to a plurality of persons simultaneously with the least network bandwidth. Unlike unicast consuming n channels for transmitting to n users, the multicast makes it possible to transmit data to n users with 1/n channels required for the unicast. Such a multicast service is capable of providing application services such as pay TV, online game, and video conference efficiently. However, since all of the users within the reception range can receive the data, there is a need of an access control technique.
Such an access control technique is implemented in the way of accomplishing the security goal of the multicast data by encrypting the multicast data and sharing a group key among the group members. In the access control technique, a Key Distribution Center (KDC) is responsible for managing the group key.
For the security of the multicast data, it is necessary to guarantee the forward secrecy after the key update and the backward secrecy before the key update and thus the KDC has to update the key when there is any change in group members due to entry and departure of group users. The frequent key updates caused by the dynamicity of the group members incur high communication and security costs.
There is therefore a need of an efficiently group key reconfiguration method for used in the wireless communication system using multicast.